Doing some work on an engine, and it may be the correct time to look at other internals.

Any way to determine when the conrod is to be replaced strictly by the manuals specifications, or is it an hours of operation or gallons of fuel ran through factor?

Are people generally referring to just the bearing when people say to replace or to “do the bottom end”?

On a properly running engine, is the conrod that measures in specification a replacement part after a certain amount of hours, or is it typical practice to just check that the conrod is within spec, and replace bearings when appropriate?

The part that fails is the bottom end bearing. They will usually last over 50 hours and I have seen them last more than 100. I have also seen them not last more than 10 hours. You can inspect it and measure the tolerances but sometimes there are no signs as to when it will fail. It is a pretty good idea to replace it after 50 hours.

Sorry, David. I didn’t mean to be so vague. The bottom end needle bearing by itself is not available from Rotax. They probably recommend changing the rod when you change the bottom end bearing. I am sure if you tried hard enough you could get the bottom end bearing. I am pretty sure Rotax doesn’t manufacture the bearing themselves.